Embodiments presented herein relate generally to electrical switchgear, and more particularly to arcless electrical switchgear.
A circuit breaker is an apparatus used to break the circuit when the current in the circuit exceeds a predefined limit. Conventional circuit breakers may produce an electrical arc when the electrical contacts open in response to a fault condition. Electrical arcing is undesirable, especially in hazardous environments where there is a danger of fires.
Some known solutions to extinguish arcing employ arc runners, arc chutes, ablative cooling, and so forth. The time taken in extinguishing the arc is very high, even greater than the contact opening time. Moreover, the arc is eliminated at natural current zero instance which occurs in AC circuit breaker. DC circuit breakers do not exhibit a natural current zero instance. Therefore, additional circuitry and arrangements are required to force a current zero instance.
One known solution utilizes a conductive liquid composition disposed in a flexible tube between the two metal contacts. During normal operating conditions, the conductive liquid composition provides low resistivity. However, when a fault condition occurs, the flexible tube is squeezed to reduce the cross section area of the tube, thus increasing the resistivity between the two metal contacts. Such an increase in the resistivity effectively creates an open circuit condition. However, such switchgear may be limited by the steady state resistivity of the conductive liquid composition. For example, due to the high conductivity of conductive liquid composition, the current conduction area may need to be reduced to 10e-6 square meter. Such a constriction may be exceedingly difficult to achieve. Further, the need for such constriction, coupled with high switching speed may warrant the use of exotic materials to produce a durable flexible tube.
Therefore, there is a need in the art for switchgear that overcomes these and other shortcomings associated with known solutions.